Cruz already had a busy first day in Congress, coming out against Sen. Dianne Feinstein's planned reintroduction of the assault weapons ban and signaling a challenge to Obama on raising the debt ceiling. The Texas Republican is also poised to play a big role in GOP politics, as a vice chairman of the National Republican Senatorial Campaign Committee.

Sen. Elizabeth Warren (D-MA)

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Warren, one of Wall Street's worst nightmares, walked through the doors of Capitol Hill Thursday and officially became a U.S. Senator after winning one of the most highly publicized election battles over Republican Scott Brown.

In the wake of the 2008 financial crisis, Warren served as the chair of the Congressional Oversight Panel and helped create the Consumer Financial Protection Bureau. She has already been handed a spot on the Senate Banking Committee, and she'll play a major role in oversight of financial institutions.

New Jersey Gov. Chris Christie

Comedy Central

Christie had a big end to 2012, and his presence should only grow as he runs for re-election and the spotlight on him gets even brighter.

This year, Christie is up for re-election, but he doesn't figure to have much of a challenge — Newark Mayor Cory Booker, his most prominent potential Democratic challenger, decided last month not to take on Christie in the gubernatorial race.

Sen. Heidi Heitkamp (D-N.D.)

AP

Like Warren, Heitkamp is a newly elected female Senator who has earned a spot on the Senate Banking Committee. She also will be a member of the Senate Agriculture Committee.

The North Dakota Senator proved herself a force to be reckoned with during her 2012 campaign, surprising everyone — including members of her own party — by how effectively she campaigned to beat her Republican opponent Rick Berg. Now, because of her position as a Democrat in a typically red state, she is poised to become an important voice in the Senate quickly.

Scott is poised to carry on the legacy of DeMint as a thorn in Obama's side from the right. His appointment also comes at a time when the Republican Party tries to rebrand itself to appeal to a broader base, and Scott, a relatively young politician, will likely play a role in that effort.

Rep. Joaquin Castro (D-Texas)

AP

Though his twin brother Julian got most of the attention in 2012, after giving the keynote speech at the Democratic National Convention, Joaquin's star has also been rising in the national party. Castro, 38, was elected to Congress for the first time in November after handily winning his Congressional race.

Castro is not stepping into just any Congressional seat — he is filling the shoes of Rep. Charlie Gonzalez, who held the 20th District's seat since 1999. Before that, Gonzalez's father, Henry, held the seat for 38 years.

Secretary of State Hillary Clinton

AP

Guessing what Clinton will do in 2016 has become the most popular parlor game in political circles. The perennially popular former First Lady plans to depart her current post as Secretary of State soon after Obama's inauguration in mid-January, and the coming 12 months could provide telling clues about her future aspirations.

In public, Clinton is saying she'll take it easy after a grueling four years. A recent concussion and subsequent hospitalization for a blood clot could be more encouragement to rest. But political observers will be watching every move she makes to get hints on what she plans to do in 2016 and to see if she can stay relevant on a national scale.

Sen. Rand Paul (R-Ky.)

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Paul has already grabbed headlines in the first few days of the year by being one of the eight Senators — along with Rubio — to oppose the deal to avert the fiscal cliff.

With his father's retirement, the younger Paul stands to inherit the growing movement of Republican libertarians. His appointment to the Senate Foreign Relations Committee, as well as his upcoming trip to Israel, has also been viewed as further signs that the Kentucky Republican is testing the waters for a 2016 presidential run.

Senate Minority Leader Mitch McConnell (R-Ky.)

McConnell started the new year off with a bang, working with Vice President Joe Biden to broker the final fiscal cliff deal. If those negotiations are any indication, McConnell will continue to play a big role in 2013, with the debt ceiling and sequester debates on the horizon.

For McConnell, this year will serve as something of a balancing act. By brokering deals on various fiscal deadlines, he sets himself up as a legislator who can work across the aisle to accomplish things. But he has to be mindful of a potential primary challenge in his 2014 re-election race if conservative Republicans grow unhappy with the deals he helps broker.

Rob Nabors, White House director of legislative affairs

Rob Nabors (left)AP

In 2011, The New Republic named Nabors one of its "most powerful, least popular" people in Washington, a title he will likely continue to live up to into 2013.

As the White House director of legislative affairs, Nabors is the President's liaison to Congress, pushing the Obama agenda through the House and Senate. That role carries a special significance in 2013 because of the legislative battles to come, over immigration, gun control, as well as fiscal issues like raising the debt ceiling and the sequester.

Scott Brown, former Republican Senator from Massachusetts

Even with Warren's grand entrance into Washington, don't expect Brown to fade away quietly. In fact, Brown could be back in the Senate as soon as this year, if he decides to run in the special election to replace Sen. John Kerry (D-Mass.), Obama's new Secretary of State nominee.

Brown has said that it would be "awfully tempting" to run, and is already setting up a potential fight against Democratic favorite Rep. Ed Markey, accusing the Massachusetts Congressman of not being an official resident of the Bay State.

Virginia Attorney General Ken Cuccinelli

AP

Cuccinelli, a Tea Party favorite, has already announced that he will run in Virginia's 2013 gubernatorial election, setting up that race to become one of the most gripping in 2013. Cuccinelli is likely set to run against Democrat Terry McAuliffe, who co-chaired President Bill Clinton's 1996 re-election campaign.

The conservative Cuccinelli, who gained a national profile by taking on Obamacare in 2010, has quickly become the the candidate of choice for Republicans. But Democrats are already prepared to attack Cuccinelli as a far-right fringe candidate in the mold of former Missouri Senate candidate Todd Akin.

Christine Quinn, New York City mayoral candidate

Quinn, the current Speaker of the New York City Council, is viewed as the frontrunner to succeed New York Mayor Michael Bloomberg, as he prepares to depart after 12 years in office.

Bloomberg has yet to endorse a candidate in the race and his enthusiasm about Quinn as his successor has appeared to wane over the past year, although he continues to praise her. Quinn, a Democrat, is the first female and first openly gay Speaker, and would be the first female and openly gay person to occupy the Mayor's office.